The long range objective of this research is to elucidate the pathophysiological mechanisms of pain in patients with interstitial cystitis (IC)in order to develop better strategies for alleviating chronic pain in these patients. IC shares many features with other chronic non-malignant visceral pain syndromes. In clinical practice much emphasis has been placed on finding a specific etiology and specific pathological markers for this disease and on identifying specific events that precipitate IC. This conceptualization has influenced clinical treatment approaches but has not resulted in significant progress so far. An additional approach is suggested, based on the conceptualization of three hypotheses: (1) a spectrum of different insults can lead to chronic visceral pain in patients suffering from IC, (2) different underlying pathogenic pain mechanisms may require different pain treatment strategies for patients diagnosed with IC, (2) different underlying pathogenic pain mechanisms may require different pain treatment strategies for patients diagnosed with IC, (3) multiple different pathogenic pain mechanisms may coexist in the same patient, requiring several different pain treatment strategies (perhaps concomitantly) to successfully treat chronic visceral pain associated with IC. This conceptualization is likely to lead to new insights into the neurophysiological mechanisms of IC and to novel treatment avenues for patients suffering from IC. As a first step towards a better understanding of the neurophysiological mechanisms of chronic pain in patients with IC we propose to characterize pain in patients with IC in detail using quantitative sensory testing, taking advantage of the typical areas of referred visceral pain, which are easily accessible to quantitative sensory testing. We hypothesize that patients with IC can be differentiated into 3 main groups based on their "sensory profiles" as assessed with quantitative sensory testing and that treatment of pain in IC will be more effective, if based on recognition of the underlying neurophysiological mechanisms. These studies will give new insights into the central and peripheral mechanisms of chronic pain in patients with IC. The results of these studies may rapidly contribute to the design of treatment strategies specifically targeted at the underlying neural mechanisms of chronic pain in patients with IC.